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Domestic electricity – WJECAlternating current and direct current

Domestic electricity explores electrical circuits and the safety devices around the home, like fuses and circuit breakers, the ring main circuit and the functions of the live, neutral and earth wires.

Part of Physics (Single Science)Electricity, energy and waves

Alternating current and direct current

Alternating current (a.c.)

If the constantly changes direction it is called alternating current, or a.c. Mains electricity is an a.c. supply. The UK mains supply is about 230 V. It has a frequency of 50 Hz, which means that it changes direction and back again 50 times a second. The diagram shows an screen displaying the signal from an a.c. supply.

An oscilloscope trace of alternating current. It shows wave shapes above and below a line labelled 0 volts.
Oscilloscope trace illustrating alternating current

Direct current electricity (d.c.)

If the current flows in only one direction it is called direct current, or d.c. Batteries and solar cells supply d.c. electricity. A typical cell or battery may supply 1.5 V. The diagram shows an oscilloscope screen displaying the signal from a d.c. supply.

Diagram showing oscilloscope trace of direct current. It is a horizontal white line on a green background.
Oscilloscope trace illustrating direct current
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